Precision Photonics Corporation proposes to develop and demonstrate the key technologies for a laser based diagnostic system for CD4+ T-cell counting in human blood. The ultimate goal is to provide very low cost, easy to use tests at the point of care to help in assessment of disease status of AIDS patients in resource limited settings. The technology will use novel diode laser illumination and ultra-sensitive detection techniques with low cost optics and lasers, analogous to a DVD sensor head. By combining sensitive detection with an immunoassay format, reagent consumption is minimized. A 2-color detection system capable of discriminating CD4+ T cells from total T cells captured on a covalently-coupled MAb grid will be developed. In the proposed project, the specific aims are to (i) develop a T cell-specific capture immunoassay on a grid, with dual label fluorescence to discriminate CD4+ from total T cells, (ii) adapt a compact diode laser imaging immunosensor platform for 2-color detection and automated cell counting, and (iii) perform proof-of-principle experiments comparing our detection method to flow cytometry, using characterized samples from collaborators. Analysis and cell counting is performed electronically, with a simple numerical readout showing both the CD4+ T cell count and CD4+ T cell percentage. The simplicity and low cost will facilitate the use of anti-retroviral therapy in resource limited settings. An internationally recognized clinical team has been assembled to take the technology into clinical trials in Phase 2. The research performed in this project, if successful, will enable very low cost, easy to use tests at the point of care to help in assessment of disease status of AIDS patients in resource limited settings. The simplicity and low cost of the technology will facilitate the use of anti-retroviral therapy, greatly prolonging the lives of those infected with HIV and reducing the burden of disease in populations where HIV is endemic. [unreadable] [unreadable] [unreadable]